This invention relates to an eye measurement system. More specifically, it relates to a system for aligning the eye of a subject for keratographic (cornea shape) measurements.
There are a number of situations where the alignment of a subject's eye is important. Various known keratographs are used to determine the cornea shape of a subject's eye. However, in order to compare the cornea shape at two different times, such as before treatment and after treatment, one must be certain that the subject's eye is aligned consistently. In other words, if one measures the cornea shape when the subject is looking to the right of an instrument axis, this measured shape will be significantly different than the shape measured if the subject's eye is looking to the left of an instrument axis.
Complete alignment information relative to an eye requires x, y and z position coordinates of a point on the eye together with three angles of the eye. The three angles may, for suitable subjects, be made consistent between two different measurements by insuring that the subject is looking in a particular direction and has his or her head upright. However, accurate cornea measurement also requires that the x, y, and z coordinates of the eye are consistent.